Following recent criticism that he was slow to name officials to his administration, Mayor-elect Vincent C. Gray on Wednesday rolled out his choices for city administrator and chief of staff.

Allen Y. Lew, czar of the District's massive school-modernization program, will take on the considerably larger role of city administrator, overseeing the day-to-day operations of city agencies, Gray (D) said at a news conference at the Reeves Municipal Center. He also named Gerri Mason Hall, a former Amtrak executive, as his chief of staff.

Over the past 15 years, Lew has overseen some of the city's largest public construction projects, including the $850 million Walter E. Washington Convention Center and $600 million-plus Nationals Park.

"It's not just his exceptional leadership over bricks and mortar. . . . The position requires someone who is a visionary and a doer," Gray said. "And frankly, the city administrator has to have a constructive level of impatience about getting things done."

Hall is a former staffer in the city's personnel office who is now a human resources executive at food services giant Sodexo.

The announcements marked a substantial development for Gray, who was criticized by some for a transition that was off to a slow start. The pace reignited worries that his career-long cautious decision-making style would mean he wouldn't be fully prepared to take over from Mayor Adrian M. Fenty (D) on Jan. 2.

The afternoon news conference followed a night and morning of buzz about Fenty appointees who received termination letters. Those let go included several young staffers, such Gabe Klein, the transportation director who became known for innovations in city government and for harnessing the changing culture of the District.

In an earlier interview, Gray said he plans to retain other Fenty staffers but would announce them later.

Although Gray and Fenty jointly announced in October that deputy schools chancellor Kaya Henderson would replace Michelle A. Rhee in an acting capacity, Lew is the highest-profile Fenty holdover so far.

Lew, an architect with a master's degree from Columbia University, has built his reputation from his days in the 1980s as acting president and chief executive of the Jacob K. Javits Convention Center Development Corp. in New York. In the District, he solidified an image as a take-charge manager while chief executive of the convention center authority and then as chief executive of the Sports and Entertainment Commission.

He and his staff are known for their no-nonsense approach to construction projects, holding contractors firm to deadlines and budgets.

In 2007, Fenty lured him to his administration as the first executive director of the Office of Public Education Facilities Modernization, an agency formed to manage the $1 billion in school building renovations and athletic field creation.